The given ratio is
Where,
Gravitational constant
Its unit is .
and Masses of electron and proton.
Their unit is kg.
Electric charge.
Its unit is C.
constant
Permittivity of free space
Its unit is .
Unit of the given ratio
Hence, the given ratio is dimensionless.
This is the ratio of electric force to the gravitational force between a proton and an electron, keeping distance between them constant.